The aim of this proposal is to develop DNA chips which can detect and characterize mutations simultaneously in the p53 tumor suppressor gene and the MSH2 and MLH1 mismatch repair genes. These chips will be used to correlate the occurrence and type of mutations in normal and tumor cells obtained from persons affected with hereditary and sporadic colorectal cancers. In Phase I, we will: 1) design/synthesize DNA chips complementary to intron/exons 5 - 8 of the p53 gene (708 bp), exons 1-16 of the msh2 gene (2727 bp) and exons 1-19 of the mlh1 gene (2268 bp), 2) develop PCR amplification strategies for either genomic (using multiplex PCR) or mRNA (using RT - PCR) copies of each of the genes, 3) develop hybridization protocols for the normal alleles for each of the three genes to measure the resequencing accuracy of the DNA chips. During Phase II, clones containing mutations for p53, MSH2 and MLH1 will serve as model targets. Detection of simple and compound heterozygotes will be demonstrated using mixtures of cloned controls. Finally, we will test the p53, MSH2 and MLH1 chips against nucleic acids obtained from previously characterized and uncharacterized patient samples (tumor tissues) in a clinical laboratory setting. PROPOSED COMMERCIAL APPLICATION: Monitoring of multiple genes which correlate with the occurrence of colorectal cancers will be necessary to identify more efficiently individuals who are at most significant risk of developing colorectal cancers either as sporadic occurrences or as a member of a family with a history of hereditary nonpolyposis colorectal cancer (HNPCC). Sporadic and HNPCC affects as many as 1 in 200 persons and is one of the most common genetic diseases in humans.